Napoli's Mertens out for three weeks with ankle sprain

The 33-year-old Belgian international limped off in the first half of Napoli's 1-0 defeat at Inter Milan on Wednesday.

"(Tests) revealed a first/second degree sprained trauma to his left ankle," Napoli said in a statement.

"Mertens has already begun rehabilitation which will continue in Belgium during the Christmas period. His condition will be re-evaluated in three weeks."

Mertens will miss Napoli's next four league games, against Lazio and Torino before Christmas and Cagliari and Spezia in the first week in January.

Gennaro Gattuso's side are fourth in Serie A, five points behind leaders AC Milan. They play Juventus in the Italian Super Cup on January 20.

Mertens has scored 130 goals for Napoli since signing from PSV Eindhoven in 2013, including five this season in all competitions.